Environmental Effects on Reproductive Health: The Endocrine Disruption Hypothesis

Abstract

R eproductive health is exquisitely sensitive to characteristics of an individual's environment-including physical, biological, behavioral, cultural and socioeconomic factors. The relative effects of these features may vary in different parts of the world or even within a country. For example, in populations with high rates of sexually transmitted diseases or in areas with inadequate health care resources, untreated infections may pose the greatest threats, increasing women's risk of experiencing premature delivery, fetal loss or prenatal mortality. Furthermore, the infants of women with such diseases risk acquiring the infection during delivery and are vulnerable to other complications during the neonatal period.' In societies where cultural norms favor large families, women may suffer health problems resulting from frequent childbearing. Similarly, malnutrition increases a pregnant woman's susceptibility to poor outcomes. In some regions, workplace and industrial pollution, as well as substances that are used commercially or in the home, may pose the greatest threats. Exposure to lead, for instance, is associated with fertility impairments in both women and men, as well as with the risk of spontaneous abortion and stillbirth; exposure to mercury in certain forms may cause birth defects and neurological disorders. A rnumber of solvents contribute to the risk of spontaneous abortion and birth defects, and some of these substances may be a factor in hypertensive disorders during pregnancy and male infertility. Epidemiological studies have proven the adverse reproductive health effects of some pesticides, and mounting evidence suggests that other of these products also are harmful to reproductive health.2 Both man-made and naturally occurring materials that appear to interfere with hormone synthesis or action are among substances whose effects on reproductive health are strongly suggested, if not clearly established. Recent research pointing to the possible role of so-called endocrine disrupters in a variety of reproductive health problems in wildlife, laboratory animals and humans has engendered considerable controversy in scientific circles. Some scientists question the valhdity of the findings on a variety of grounds, while others have used them to outline agendas for further research and relevant policymaking. As the endocrine disruption debate continues to occupy researchers, it also is gaining attention among the public. During the past several years, articles and opinion pieces about reproductive health problems and endocrine disruption have appeared in newspapers and in popular science, business, news and general interest magazines.3 Public interest groups have produced monographs reviewing the subject,4 and the trade publications of industries whose products have been labeled endocrine disrupters have carried articles and editorials seeking a balanced reading of the evidence.5 A new round of coverage followed the publication in early 1996 of Our Stolen Future: Are We Threatening Our Fertility, Intelligence, and Survival?-A Scientific Detective Story.6 The book, written for lay readers, chronicles the development of the endocrine disruption hypothesis and considers its implications. Much of the popular coverage of the issue has reflected great attention to presenting both sides of the question in a manner that will inform but not alarm the public. Some of it, however, has been less successful at establishing a context for the findings, clearly distinguishing facts from hypotheses, and communicating a measured view of the implications both of what has been demonstrated and of areas requiring extensive additional research. The public has a right and a need to know about issues with a potential for substantial public health ramifications; sensible voices on both sides of this debate acknowledge the need for additional research and risk assessment, clear priorities for dealing with documented risks and dissemination of verifiable information that can help individuals make informed health decisions. The endocrine disruption hypothesis promises to remain a focus of researchand debate-for some time to come. Therefore, without minimizing the importance of other environmental risk factors for men's and women's reproductive health, this report focuses on what is known about hormone disrupters, areas that are being explored and the potential implications for public health and policy.